#include <iostream>
#include <iomanip>

using namespace std;

int main()
{
    double n = 0;
    int k = 0;
    cin >> n >> k;
    double temp = 0.00;
    if (k % 2 == 0)
        temp = n * n / ((k / 2 + 1) * (k / 2 + 1));
    else
        temp = n * n / (((k - 1) / 2 + 1) * ((k - 1) / 2 + 2));
    cout << fixed << setprecision(2) << temp << endl;
    return 0;
}